A state-of-the-art SQUID system will be used to measure the visually evoked magnetic field of the human brain. These measures will be compared with visually evoked potentials. The proposal describes recent results indicating that the visualy evoked field exhibits two amplitude maxima over two spatially distinct regions along the midline. Responses from these small regions differ in phase by about 90 degrees and not 180 degrees, as would be expected if a single equivalent current dipole produced the detected fields. In one of these regions the response latency increases with spatial frequency. This increase in latency correlates with reaction time to the same stimuli. This is consistent with the notion that two populations of cells contribute to the response. Spatial frequency of the stimulus was found to interact with temporal frequency of presentation. The following experiments are proposed to: a) compare the visually evoked field (VEF) with the visually evoked potential (VEP); b) generate spatio-temporal maps of the VEF and VEP with stimuli of different temporal frequency, spatial frequency, contrast, average luminance and position of the stimulus in the visual field; c) improve our technologgy to permit recovery of the transient VEF in a normal laboratory environment; d) compare the latency of the transient VEF to that computed from the phase-trends of the steady-state VEF; e) determine if an abrupt change in the phase trends of VEFs is related to the perception of smooth unidirectional apparent movement of contrast reversal gratings; f) measure the difference in spatial frequency of dichoptically presented components of compound gratings required to elicit independent (superimposable) responses; g) measure the difference in orientation of superimposed gratings at which the gratings produce independent responses.